bauble::utils::pyparsing::Forward Class Reference

Detailed Description

Forward declaration of an expression to be defined later -
used for recursive grammars, such as algebraic infix notation.
When the expression is known, it is assigned to the Forward variable using the '<<' operator.
Note: take care when assigning to Forward not to overlook precedence of operators.
Specifically, '|' has a lower precedence than '<<', so that::
fwdExpr << a | b | c
will actually be evaluated as::
(fwdExpr << a) | b | c
thereby leaving b and c out as parseable alternatives. It is recommended that you
explicitly group the values inserted into the Forward::
fwdExpr << (a | b | c)